328 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



After this no additions were made for seventeen years, when Dr. 

 W. H. Dall described Cerithiopsis stejnegeri, from Alaska. 1 Two years 

 later the same author added another species, 2 also from Alaska, under 

 the name Cerithiopsis stejnegeri truncata. 



After another lapse of seventeen years we find another species 

 added to our list, this time a fossil described as Bittium williamsoni 

 by Dr. Ralph Arnold, 3 from the Pleistocene beds of San Pedro and San 

 Diego, California. Five } T ears later the present writer described: 4 



Bittium tumidum. Cerithiopsis cosmia. 



Bittium quadrifilatum ingens. Cerithiopsis pedroana. 



the first two of which must be referred to the present genus. Since 

 then Doctor Dall has added Cerithiopsis excelsus, 5 and the present 

 writer described Cerithiopsis stephensse. 6 



The nuclear characters of the species studied are quite interesting 

 and can be used to advantage in subdividing the genus into minor 

 groups. Unfortunately, twenty of the forty-five forms under consid- 

 eration have lost these early turns, which leaves a rather large per- 

 centage in an uncertain position. 



Of the twenty-five species in which the nuclear whorls are known, 

 eighteen belong to Cerithiopsis proper, having smooth nuclear whorls. 

 These are: 



fatua Bartsch. dbreojosensis Bartsch. 



oxys Bartsch. berryi Bartsch. 



cerea Carpenter. galapagensis Bartsch. 



sorex Carpenter. cesta Bartsch. 



carpenteri Bartsch. stejnegeri Dall. 



pedroana Bartsch. stejnegeri dina Bartsch. 



tuberculides Carpenter. neglecta C. B. Adams. 



tuberculides albonodosa Carpenter. halia Bartsch. 



pupiformis Carpenter. aurea Bartsch. 



Two species have the early portion of the nuclear whorls smooth 

 and the later part axially ribbed ; for these I would suggest the sub- 

 generic name CeritMopsina. The two species are Cerithiopsis 

 (Cerithiopsina) necropolitana Bartsch and Cerithiopsis (CeritMopsina) 

 adamsi Bartsch. The first of these may be considered the type. 



Two species have the early portion of the nuclear whorls smooth, 

 which is succeeded by an axially ribbed part, which in turn is fol- 

 lowed by a portion bearing two spiral cords in addition to the axial 

 ribs. The last ornamentation resembles the sculpture of the early 

 post-nuclear whorls, but is less strong, with many more axial ribs 



' Proc. U. S. Nat. Mus., vol. 7, 1S84, pp. 345-6, pi. 2, fig. 4. 



2 Proc. U. S. Nat. Mus., vol. 9, 1886, p. 304, pi. 4, fig. 5. 



8 Mem. California Acad. Sci., vol. 3, 1903, p. 295, pi. 6, fig. 11. 



* Proc. U. S. Nat. Mus., vol. 33, 1907, pp. 79-82. 



6 Prof. Paper No. 59, U. S. Geol. Surv., 1909, p. 75. 



6 Proc. U. S. Nat. Mus.. vol. 37, 1909, pp. 399-400 and figure. 



